Question

Careful measurement of the electric field at the surface of a black
box indicates that the net outward flux through the surface of the
box is 8.0 x 109 Nm²/C. (a) What is the net charge inside the box?
(b) If the net outward flux through the surface of the box were zero,
could you conclude that there were no charges inside the box? Why
or Why not?​

Answer 1

Explanation:

(a) q=ϵ

0

Φ=8.85×10

−12

×8×10

3

C=0.07μC

(b) No. Net flux piercing out through a body depends on the net charge contained in the body. If net flux is zero, then it can be inferred that net charge inside the body is zero. The body may have equal amount of positive and negative charges.

Hope this answer helps you...

Answer 2

Answer:

A) From Gauss law, Flux = Q(inclosed) /Epsilon not

Therefore, Q(inclosed) = 8 × 10^9 × 8.854187817 × 10⁻¹² = 70.8 × 10^-3

B) No, it is not always true. Such conditions can occur when Net charge inclosed is zero. E.g in case of Dipole. Since, in dipole both charges are equal & opposite, Net charge is zero.

Hope you understand.